Comparative Assessment of Antimicrobial Resistance in Poultry-Associated Escherichia coli between Commercial and Backyard Poultry Systems in Chattogram, Bangladesh

Abstract

Background: Poultry-associated Escherichia coli is a critical reservoir of multidrug resistance (MDR), posing escalating zoonotic risks at the human-animal interface. Comparative risk assessment of MDR E. coli between commercial farm and backyard systems remains understudied in Chattogram, Bangladesh. Objective: This study comparatively assessed the bacterial load, antimicrobial resistance profiles, and MDR burden of E. coli in poultry litter samples from both production systems. Method: Bacterial load was evaluated, followed by biochemical tests to identify probable bacterial species, and E. coli identification through culture and polymerase chain reaction. Additionally, the antimicrobial sensitivity pattern of E. coli to antimicrobial agents was determined using the disk diffusion method. Descriptive statistical analysis was performed to assess the association of knowledge and practice of antimicrobial agents across sources. Results: Farm and backyard samples yielded mean bacterial loads of 141.78 and 134.74 Colony-Forming Units per milliliter, respectively. Both systems harbored overlapping yet compositionally distinct MDR bacterial communities, with Acinetobacter exclusively recovered from backyard samples. Furthermore, universal ampicillin and tetracycline resistance (100%) was observed in farm isolates, with predominant ciprofloxacin resistance, while backyard isolates retained broader gentamicin susceptibility. Descriptive analysis revealed that antibiotic full-dose completion was observed in 92.6% of farms, whereas it was observed in 19.1% of backyard systems. Some respondents from both systems reported concurrent illnesses in humans and chickens following the use of human medicines in poultry. Conclusion: These findings necessitate production-system-specific stewardship strategies and integrated One Health surveillance frameworks to mitigate MDR E. coli transmission in high-density poultry production regions.